在Arduino上调制脉冲宽度时有奇怪的声音

但它发出的声音和我预想的不一样。

我的代码是:

class Phasor
{
public:
    Phasor(const float frequency)
    :frequency(frequency)
    ,phase(1.0f)
    ,lastTimeMicros(0){};
    virtual ~Phasor(){};
    void setFrequency(const float frequency)
    {
        this->frequency = frequency;
    }
    float process()
    {
        const unsigned long currentTimeMicros = micros();
        if (phase == 1.0f) lastTimeMicros = currentTimeMicros;
        const unsigned long elapsedTimeMicros = currentTimeMicros - lastTimeMicros;
        const unsigned long cycleDurationMicros = static_cast<unsigned long>(1000.0f / frequency) * 1000;
        if (elapsedTimeMicros < cycleDurationMicros)
            phase = static_cast<float>(elapsedTimeMicros) / static_cast<float>(cycleDurationMicros);
        else
            phase = 1.0f;
        return phase;
    }
private:
    float frequency;
    float phase;
    unsigned long lastTimeMicros;
};

class PulseOsc
{
public:
    PulseOsc(const float frequency, const float pulseWidth)
    :phasor(frequency)
    ,pulseWidth(pulseWidth){};
    virtual ~PulseOsc(){};
    void setFrequency(const float frequency)
    {
        this->phasor.setFrequency(frequency);
    }
    void setPulseWidth(const float pulseWidth)
    {
        this->pulseWidth = pulseWidth;
    }
    float process()
    {
        const float phase = phasor.process();
        if (phase <= pulseWidth)
            return 1.0f;
        else
            return -1.0f;
    }
private:
    Phasor phasor;
    float pulseWidth;
};

Phasor *phasorLFO;
PulseOsc *pulseOsc;

void setup()
{
    Serial.begin(9600);
    pinMode(9, OUTPUT);
    phasorLFO = new Phasor(0.1f);
    pulseOsc = new PulseOsc(440.0f, 0.5f);
}

void loop()
{
    pulseOsc->setPulseWidth(phasorLFO->process());
    int outVal = LOW;
    if (pulseOsc->process() > 0.0f) outVal = HIGH;
    digitalWrite(9, outVal);
}

由此产生的声音非常怪异和不连贯。

我的代码怎么了?